package com.login.encryption;

import java.security.AlgorithmParameters;
import java.security.SecureRandom;
import java.security.spec.KeySpec;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

public class SecurityUtils {

	
	private static final byte[] salt = {
		(byte)0xA4, (byte)0x0B, (byte)0xC8, (byte)0x34,
		(byte)0xD6, (byte)0x95, (byte)0xF3, (byte)0x13
	};
	
	private static int BLOCKS = 128;
	
	public static byte[] encryptAES(String seed, String cleartext) throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes("UTF8"));
		SecretKeySpec skeySpec = new SecretKeySpec(rawKey, "AES");
		Cipher cipher = Cipher.getInstance("AES");
	    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
	    return cipher.doFinal(cleartext.getBytes("UTF8"));
	}
	
	public static byte[] decryptAES(String seed, byte[] data) throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes("UTF8"));
	    SecretKeySpec skeySpec = new SecretKeySpec(rawKey, "AES");
		Cipher cipher = Cipher.getInstance("AES");
	    cipher.init(Cipher.DECRYPT_MODE, skeySpec);
	    return cipher.doFinal(data);
	}

	private static byte[] getRawKey(byte[] seed) throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
		sr.setSeed(seed);
	    kgen.init(BLOCKS, sr); // 192 and 256 bits may not be available
	    SecretKey skey = kgen.generateKey();
	    byte[] raw = skey.getEncoded();
	    return raw;
	}
	
	private static byte[] pad(byte[] seed)
	{
		byte[] nseed = new byte[BLOCKS/8];
		for(int i=0; i < BLOCKS/8; i++)
			nseed[i]=0;
		for(int i=0; i < seed.length; i++)
			nseed[i] = seed[i];
			
		return nseed;
	}
	
	public static byte[] encryptPBE(String password, String cleartext) throws Exception
	{
		SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
		KeySpec spec = new PBEKeySpec(password.toCharArray(), salt, 1024, 256);
		SecretKey tmp = factory.generateSecret(spec);
		SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");

		Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
		cipher.init(Cipher.ENCRYPT_MODE, secret);
		AlgorithmParameters params = cipher.getParameters();
		byte[] iv = params.getParameterSpec(IvParameterSpec.class).getIV();
		return cipher.doFinal(cleartext.getBytes("UTF-8"));
	}
	
	public static String decryptPBE(SecretKey secret, String ciphertext, byte[] iv)  throws Exception
	{
		Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
		cipher.init(Cipher.DECRYPT_MODE, secret, new IvParameterSpec(iv));
		return new String(cipher.doFinal(ciphertext.getBytes()), "UTF-8");
	}
	
}
